Remove __need_IOV_MAX and __need_FOPEN_MAX.

Remove __need_IOV_MAX and __need_FOPEN_MAX.

__need_FOPEN_MAX wasn't being used anywhere.  __need_IOV_MAX was more
complicated; the basic deal is that sys/uio.h wants to define a
constant named UIO_MAXIOV and bits/xopen_lim.h wants to define a
constant named IOV_MAX, with the same meaning.  For no apparent reason
this was being handled via bits/stdio_lim.h -- stdio.h is NOT supposed
to define IOV_MAX -- and some mess in Makerules.  Also, bits/uio.h on
Linux was being used as a dumping ground for extension functions.

So now we have bits/uio_lim.h, which defines __IOV_MAX.
bits/xopen_lim.h and sys/uio.h use that to define their respective
constants.  We also now have bits/uio-ext.h, which is the official
Proper Home for extensions to sys/uio.h.  bits/uio.h is removed, and
stdio_lim.h doesn't define IOV_MAX at all.

	* bits/uio_lim.h, sysdeps/unix/sysv/linux/bits/uio_lim.h
	* bits/uio-ext.h, sysdeps/unix/sysv/linux/bits/uio-ext.h: New file.
	* bits/uio.h, sysdeps/unix/sysv/linux/bits/uio.h: Delete file.

	* include/bits/xopen_lim.h: Use bits/uio_lim.h to get the value
	for IOV_MAX.
	* misc/Makefile: Install bits/uio-ext.h and bits/uio_lim.h.
	Don't install bits/uio.h.
	* misc/sys/uio.h: Don't include bits/uio.h.  Do include
	bits/types/struct_iovec.h and bits/uio_lim.h.  Set UIO_MAXIOV
	based on __IOV_MAX. Under __USE_GNU, also include bits/uio-ext.h.

	* stdio-common/stdio_lim.h.in: Remove logic for __need_FOPEN_MAX
	and __need_IOV_MAX.  Don't define IOV_MAX at all.
	* Makerules (stdio_lim.h): Remove logic for setting IOV_MAX.

	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
	Include bits/types/struct_iovec.h, not bits/uio.h.
	Use __ssize_t, not ssize_t, in function prototypes.
	Don't use hard TAB for double space after period in comments.